Hi @headcases said, you will have to set up another account to do that. The rule here is that each SIM is tied to a unique account with a different 'user name'. I have two SIMs myself, one in a spare phone. Different accounts can share the same email address, same bank or credit card details etc., the only thing that must be different is the account name.
Also, be careful on the community. You are allowed only one account here, although the other new account could be used you will be penalised if they find out it's the same person. They don't want you 'bigging yourself up' across two accounts!
For a 'data only SIM' you will only want to buy gigabags. Don't make the rookie mistake of confusing them with goodybags.